This invention relates to toilets. More particularly it relates to toilets having moveable trapways to facilitate bowl evacuation with reduced water usage.
Conventional toilets typically have a bowl portion connected to a trapway. One such prior art toilet 10 is shown in FIG. 1 of this application. A trapway 12 extends from a bowl 14 to an outlet 16. In conventional fashion the trapway 12 slopes upwardly as it extends away from the bowl opening 18 such that the trapway 12 forms a weir or water dam 20. The weir 20 prevents downstream sewer gases from returning to the toilet. This is because when the toilet 10 is not in use the water level will be as shown as in the dotted lines, thereby preventing gases from returning from the outlet 16 back to the bathroom.
When the toilet is flushed by adding more water to the bowl, as is well known in the art, the configuration of the weir 20, the down leg 22, the elbow 24, and the out leg 26, induces the formation of a siphon that assists the evacuation of water and waste from the bowl 14. The trapway 12 then transports the waste to the outlet 16 and an attached sewer line.
However, a structure that promotes the formation of a siphon requires some design compromises. For example, the smaller the cross section of the trap, the easier it is to form the siphon. On the other hand, small cross section traps may be susceptible to clogging, and in any event at the extreme may violate plumbing codes.
Further, toilets which rely on siphons can “waste” at least some water to develop the siphon. This can be problematic given the regulatory restrictions on using more than 6.06 liters per flush, and given the market preference for even more “green friendly” toilets.
Achieving an effective flush, while using so little water, can be difficult. A variety of different approaches have been tried (e.g. pressurizing the water; using jets). However, each known approach has its disadvantages. For example, some approaches add undesirable costs. Others rely on systems that don't clean certain types of waste as effectively, leading consumers to flush twice or more.
Some approaches have tried to move the trapway during the flush cycle, while still relying on some form of siphon development. For example, U.S. Pat. No. 3,922,729 provides a toilet that initiates an emptying of bowl by lowering a dam made from a flexible material. However, this toilet still has a lower trapway portion for formation of a siphon and creation of a water seal.
Another approach is to move the trapway during the flush cycle, and not rely on a siphon. For example, U.S. Pat. No. 2,817,092 shows a portable commode with moveable components and does not require the formation of a siphon. However, the length of the flush cycle is variable and conditioned on the length of time that a handle is depressed by the user. Thus, the flush cycle is not readily reproducible, nor guaranteed to meet regulatory requirements restricting the amount of water used per flush cycle.
Likewise, U.S. Pat. No. 5,446,928 does not require the formation of a siphon. However, it does require the user to lift the entire seat and bowl of the toilet to straighten a tube trapway.
U.S. Pat. No. 6,195,810 has a flexible trapway that is controlled by an electric motor to position a moveable trapway for the elimination of waste from the bowl. However, such a trapway requires electrical power to operate the toilet regardless of the advantages this structure might otherwise have.
Other U.S. patent documents representative of the art with respect to moveable trapways include U.S. Pat. Nos. 270,211, 2,678,450, 3,302,216, 3,521,305, 3,585,650, 3,922,729, 4,028,746, 4,947,492 and 6,467,101, and U.S. patent application publications 2001/0049841, 2001/0052147, 2002/0112283 and 2002/0124302.
Accordingly, there is still a need for improved trapways, particularly those which permit efficient bowl cleaning with very low levels of water usage per flush.